Elemental phosphorus may be formed by electric reduction of phosphate rock. In a particular known procedure, ground and pelletized phosphate rock ore is mixed with coke and silica, and the mixture is electrically smelted. The phosphorus is driven off in gaseous form, condensed and recovered as a liquid. The liquid phosphorus is collected under water since it is combustible when exposed to air.
Liquid waste effluents are provided by this procedure including condensor process water, called "phossy" water. The phossy water contains small quantities of elemental phosphorus , and, after smelting together with other aqueous effluents in a first pond, the resulting aqueous liquid contains from about 3 to 10 ppm. After further lowering of the elemental phosphorus content in scrubbing operations the aqueous liquid is treated with lime to a pH of about 5.5 in a second pond. The resulting pond effluent, known as No. 2 pond water, contains from about 5 to 10 ppb of elemental phosphorus.
Phosphorus has been found to be toxic to aquatic life, especially marine fish, and hence, from an environmental protection point of view, the discharge of the phossy water to aquatic life-bearing water bodies should be avoided.
Due to the colloidal nature of the suspension of the elemental phosphorus in the No. 2 pond water, it is extremely difficult to separate out the solid elemental phosphorus by physical methods, such as filtration and centrifuging. In addition, simple dilution of this waste effluent is ineffective since the elemental phosphorus tends to accumulate at the discharge point of the waste water rather than being dispersed.
The present invention makes it possible to decrease the elemental phosphorus content of aqueous media below an undetectable level (i.e., less than 0.1 ppb), and hence allowing the safe discharge of the treated aqueous medium to water bodies.